Consolidated Income Statements - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Revenues	$ 1,318,641	$ 1,170,026	$ 971,191
Operating expenses:
Selling, general and administrative expenses	382,389	382,676	323,270
Acquisition-related costs	777	5,093	38,272
Depreciation and amortization expenses	70,501	66,614	52,694
Gain on disposition of property, plant and equipment	(1,107)	(2,731)	(1,656)
Impairment loss	0	0	8,911
Foreign exchange (gain) loss	(2,937)	(212)	2,559
Total operating expenses	1,095,439	984,837	863,737
Operating income	223,202	185,189	107,454
Interest expense	(41,277)	(44,527)	(38,291)
Other income, net	8,838	11,850	8,231
Income before income taxes	190,763	152,512	77,394
Current income tax	32,797	24,767	19,356
Deferred income tax	8,826	6,239	(17,268)
Income tax expense (recovery)	41,623	31,006	2,088
Net income	149,140	121,506	75,306
Net income attributable to:
Stockholders	149,039	121,479	75,027
Non-controlling interests	101	27	279
Net income	$ 149,140	$ 121,506	$ 75,306
Earnings per share attributable to stockholders:
Basic	$ 1.37	$ 1.12	$ 0.70
Diluted	$ 1.36	$ 1.11	$ 0.69
Weighted average number of shares outstanding:
Basic	108,519,739	108,063,349	107,044,348
Diluted	109,759,123	109,388,236	108,113,151
Service Revenue [Member]
Revenues:
Revenues	$ 804,024	$ 749,515	$ 624,417
Operating expenses:
Direct expenses	164,977	159,058	133,189
Inventory Sales Revenue [Member]
Revenues:
Revenues	514,617	420,511	346,774
Operating expenses:
Direct expenses	$ 480,839	$ 374,339	$ 306,498